• Bunker
  Bunker
  A military bunker is a hardened shelter, often buried partly or fully underground, designed to protect the inhabitants from falling bombs or other attacks...
  
  
• Casemate
  Casemate
  A casemate, sometimes rendered casement, is a fortified gun emplacement or armored structure from which guns are fired. originally a vaulted chamber in a fortress.-Origin of the term:...
  
  
• Catacombs
• Cave
  Cave
  A cave or cavern is a natural underground space large enough for a human to enter. The term applies to natural cavities some part of which is in total darkness. The word cave also includes smaller spaces like rock shelters, sea caves, and grottos.Speleology is the science of exploration and study...
  
  s
  • Ice cave
    Ice cave
    The term ice cave refers to any type of natural cave that contains significant amounts of perennial ice...
    
    s
• Cave dwellings, Cave house
• Cave temple
• Cellar
  Basement
  __FORCETOC__A basement is one or more floors of a building that are either completely or partially below the ground floor. Basements are typically used as a utility space for a building where such items as the furnace, water heater, breaker panel or fuse box, car park, and air-conditioning system...
  
  
• Cenote
  Cenote
  A cenote is a deep natural pit, or sinkhole, characteristic of Mexico and Central America, resulting from the collapse of limestone bedrock that exposes groundwater underneath...
  
  
• Dungeon
  Dungeon
  A dungeon is a room or cell in which prisoners are held, especially underground. Dungeons are generally associated with medieval castles, though their association with torture probably belongs more to the Renaissance period...
  
  
• Dugout (shelter)
  Dugout (shelter)
  A dugout or dug-out, also known as a pithouse, pit-house, earth lodge, mud hut, is a shelter for humans or domesticated animals and livestock based on a hole or depression dug into the ground. These structures are one of the most ancient types of human housing known to archeologists...
  
  
• Karst
  KARST
  Kilometer-square Area Radio Synthesis Telescope is a Chinese telescope project to which FAST is a forerunner. KARST is a set of large spherical reflectors on karst landforms, which are bowlshaped limestone sinkholes named after the Kras region in Slovenia and Northern Italy. It will consist of...
  
  
• Gallery
  Long gallery
  Long gallery is an architectural term given to a long, narrow room, often with a high ceiling. In British architecture, long galleries were popular in Elizabethan and Jacobean houses. They were often located on the upper floor of the great houses of the time, and stretched across the entire...
  
  
• Lava tube
  Lava tube
  Lava tubes are natural conduits through which lava travels beneath the surface of a lava flow, expelled by a volcano during an eruption. They can be actively draining lava from a source, or can be extinct, meaning the lava flow has ceased and the rock has cooled and left a long, cave-like...
  
  s
• Lunar lava tube
  Lunar lava tube
  Lunar lava tubes are sub-surface tunnels on the Moon that are believed to have formed during basaltic lava flows. When the surface of a lava tube cools, it forms a hardened lid that contains the ongoing lava flow beneath the surface in a conduit-shaped passage. Once the flow of lava diminishes, the...
  
  
• Rock cut architecture
  Rock cut architecture
  Rock-cut architecture is the practice of creating buildings and other physical structures by carving natural rock. In India the term 'cave' is often applied, and in China 'cavern,' but one must differentiate natural caves from rock-cut architecture which is man-made and designed along the...
  
  , rock grave
• Subterranean river
  Subterranean river
  A subterranean river is a river that runs wholly or partly beneath the ground surface – one where the riverbed does not represent the surface of the Earth ....
  
  s
• Tunnel
  Tunnel
  A tunnel is an underground passageway, completely enclosed except for openings for egress, commonly at each end.A tunnel may be for foot or vehicular road traffic, for rail traffic, or for a canal. Some tunnels are aqueducts to supply water for consumption or for hydroelectric stations or are sewers...
  
  s (street tunnel, train tunnels)
• Underground city
  Underground city
  An Underground city is a series of linked subterranean spaces that may provide a defensive refuge; a place for living, working or shopping; a transit system; mausolea; wine or storage cellars; cisterns or drainage channels; or several of these. The term may also refer to a network of tunnels that...
  
  
• Underground lake
  Underground lake
  An underground lake or a subterranean lake is a lake under the surface of the Earth's crust. Such a lake may be associated with caves, aquifers, or springs. They are typically very low in salinity....
  
  s
• Underground rapid transit systems
• Volcanic pipe
  Volcanic pipe
  Volcanic pipes are subterranean geological structures formed by the violent, supersonic eruption of deep-origin volcanoes. They are considered to be a type of diatreme. Volcanic pipes are composed of a deep, narrow cone of solidified magma , and are usually largely composed of one of two...
  
  s
• Wine cave
  Wine cave
  Wine caves are subterranean structures for the storage and aging of wine. They are an integral component of the wine industry world wide. The design and construction of wine caves represents a unique application of underground construction techniques....
  
  s

See also

• Subterranean London
  Subterranean London
  The metropolis of London has been occupied for millennia, and has over that time acquired a large number of subterranean structures.These have served a number of purposes:-Water and waste:Since its foundation, the Thames has been at the heart of London...
  
  
• Seattle Underground
  Seattle Underground
  The Seattle Underground is a network of underground passageways and basements in downtown Seattle, Washington, United States that was ground level at the city's origin in the mid-19th century. After the streets were elevated these spaces fell into disuse, but have become a tourist attraction in...